Lock-up device for torque converter

ABSTRACT

A lock-up device includes a clutch portion, a piston, a sleeve and an oil chamber plate. The clutch portion is disposed between the front cover and a turbine. The piston is movable in an axial direction. The piston turns the clutch portion into a torque transmission state. The sleeve is fixed to a front cover and includes an outer peripheral surface and a protrusion. The outer peripheral surface supports an inner peripheral surface of the piston such that the piston is movable in the axial direction. The protrusion has an annular shape and protrudes radially outward from the outer peripheral surface. The oil chamber plate has a disc shape and is joined to a piston-side lateral surface of the protrusion of the sleeve. The oil chamber plate defines an oil chamber together with the piston therebetween. The oil chamber is supplied a hydraulic oil for activating the piston.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No.2016-055067 filed on Mar. 18, 2016, the entirety of which is herebyincorporated by reference in its entirety.

BACKGROUND

Technical Field

The present disclosure relates to a lock-up device, and particularly toa lock-up device for a torque converter, which is configured to transmita torque from a front cover to a transmission-side member through aturbine.

Background Information

Torque converters are often equipped with a lock-up device for directlytransmitting a torque from a front cover to a turbine. Such a lock-updevice includes a piston, an input-side plate, a plurality of torsionsprings, and an output-side plate. The piston is capable of beingcoupled by friction to the front cover. The input-side plate is fixed tothe piston. The torsion springs are supported by the input-side plate.The output-side plate is elastically coupled through the torsion springsto the piston and the input-side plate in a rotational direction. Theoutput-side plate is fixed to the turbine.

Additionally, as described in Japan Laid-open Patent ApplicationPublication No. 2013-217452, a type of lock-up device has been alsoproposed in which a plurality of friction facings are used to increaseits clutch capacity.

In the lock-up device described in Japan Laid-open Patent ApplicationPublication No. 2013-217452, a clutch plate is disposed between thefront cover and the turbine. A lock-up state (power transmission state)is herein made when the clutch plate is contacted to the front cover andthe piston while being pressed therebetween. In this state, a torquefrom the front cover is directly transmitted to the turbine withoutthrough a torque converter body.

In the lock-up device described in Japan Laid-open Patent ApplicationPublication No. 2013-217452, an oil chamber plate is disposed betweenthe piston and the turbine, and an oil chamber for activating the pistonis defined between the piston and the oil chamber plate. The innerperipheral end of the oil chamber plate is fixed by welding to the outerperipheral surface of a sleeve-shaped boss fixed to the front cover.

In this construction, when hydraulic oil is supplied to the oil chamber,a force acts on the oil chamber plate in a direction separating from thepiston. When the oil chamber plate is deformed by the force, chances arethat the aforementioned space defined between the piston and the oilchamber plate does not function as the oil chamber. Additionally,deformation of the oil chamber plate bears a risk of damage or breakagethereof. Therefore, the oil chamber plate is required to have a largethickness to enhance its stiffness.

BRIEF SUMMARY

It is an object of the present disclosure to inhibit deformation of anoil chamber plate composing part of an oil chamber for activating apiston with a simple construction.

(1) A lock-up device for a torque converter according to the presentdisclosure is a device configured to transmit a torque from a frontcover to a transmission-side member through a turbine. The lock-updevice includes a clutch portion, a piston, a sleeve and an oil chamberplate. The clutch portion is disposed between the front cover and theturbine. The piston is disposed to be movable in an axial direction. Thepiston is configured to turn the clutch portion into a torquetransmission state. The sleeve is fixed to the front cover and includesan outer peripheral surface and a protrusion. The outer peripheralsurface supports an inner peripheral surface of the piston such that thepiston is movable in the axial direction. The protrusion has an annularshape and protrudes radially outward from the outer peripheral surface.The oil chamber plate has a disc shape and defines an oil chambertogether with the piston therebetween. The oil chamber is configured tobe supplied a hydraulic oil for activating the piston. Additionally, theoil chamber plate is joined to a piston-side lateral surface of theprotrusion of the sleeve.

In the lock-up device, when the hydraulic oil is supplied to the oilchamber, the piston is configured to be moved in the axial direction,and thereby, the clutch portion is configured to be turned into thetorque transmission state.

When the hydraulic oil is herein supplied to the oil chamber, the oilchamber plate receives a force acting in a direction separating from thepiston by the hydraulic pressure generated in the oil chamber. However,the inner peripheral part of the oil chamber plate is herein joined tothe piston-side lateral surface of the sleeve. Hence, the oil chamberplate is supported by the protrusion of the sleeve in a directionopposite to the direction of the force acting on the oil chamber plate.Therefore, deformation of the oil chamber plate can be inhibited.

(2) The oil chamber plate may be joined at an inner peripheral partthereof to the protrusion of the sleeve by welding.

(3) The oil chamber plate may include a tubular part. The tubular partsupports an outer peripheral surface of the piston such that the pistonis movable. In this construction, the oil chamber can be composed of asmall number of components.

(4) The lock-up device may further include seal members. One of the sealmembers is mounted between the inner peripheral surface of the pistonand the outer peripheral surface of the sleeve, whereas the other of theseal members is mounted between the outer peripheral surface of thepiston and an inner peripheral surface of the tubular part of the oilchamber plate. Additionally, the sleeve may include an oil channel forsupplying the hydraulic oil to the oil chamber.

(5) The lock-up device may further include a drive hub fixed to thesleeve. Additionally, the piston may include an engaging part. Theengaging part is engaged with part of the drive hub. The piston may beconfigured to be rotated in synchronization with the drive hub.

The piston and the sleeve to which the drive hub is fixed are hereinconfigured to be rotated in synchronization with each other. In otherwords, relative rotation does not occur between the piston and thesleeve. Therefore, abrasion of the piston and the sleeve can beprevented. Additionally, when the seal member is mounted between thepiston and the sleeve, abrasion of the seal member can be inhibited.

As described above, according to the present disclosure, deformation ofan oil chamber plate composing part of an oil chamber for activating apiston can be inhibited with a simple construction.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the attached drawings which form a part of thisoriginal disclosure:

FIG. 1 is a cross-sectional view of a torque converter including alock-up device according to a preferred embodiment of the presentdisclosure;

FIG. 2 is a diagram extracted from FIG. 1 and shows a part forsupporting a clutch portion and a piston;

FIG. 3 is a partial front view of the piston;

FIG. 4 is a diagram extracted from FIG. 1 and shows a damper portion;

FIG. 5 is a diagram of a positioning structure of the damper portion;and

FIG. 6 is a chart showing torsional characteristics of the lock-updevice.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 is a partial cross-sectional view of a torque converter 1including a lock-up device according to a preferred embodiment of thepresent disclosure. In FIG. 1, an engine (not shown in the drawing) isdisposed on the left side whereas a transmission (not shown in thedrawing) is disposed on the right side. It should be noted that line O-Odepicted in FIG. 1 indicates a common rotational axis for the torqueconverter 1 and the lock-up device. It should be also noted that in thefollowing explanation, the term “radial direction” refers to a directionseparating from the rotational axis whereas the term “axial direction”refers to a direction arranged along the rotational direction.

(Entire Construction of Torque Converter 1)

The torque converter 1 is a device configured to transmit a torque froman engine-side crankshaft (not shown in the drawings) to an input shaftof the transmission. As shown in FIG. 1, the torque converter 1 iscomposed of a front cover 2, a torque converter body 6 and a lock-updevice 7.

The front cover 2 is fixed to an input-side member. The front cover 2 isa substantially disc-shaped member, and its outer peripheral partprotrudes toward the transmission as an outer peripheral tubular part10.

The torque converter body 6 is composed of three types of bladed wheels(an impeller 3, a turbine 4 and a stator 5).

The impeller 3 is composed of an impeller shell 12, a plurality ofimpeller blades 13 and an impeller hub 14. The impeller shell 12 isfixed to the outer peripheral tubular part 10 of the front cover 2 bywelding. The impeller blades 13 are fixed to the inside of the impellershell 12. The impeller hub 14 has a tubular shape and is disposed on theinner peripheral side of the impeller shell 12.

The turbine 4 is disposed in opposition to the impeller 3 within a fluidchamber. The turbine 4 is composed of a turbine shell 15, a plurality ofturbine blades 16 and a turbine hub 17. The turbine blades 16 are fixedto the inside of the turbine shell 15. The turbine hub 17 is fixed tothe inner peripheral part of the turbine shell 15. The turbine hub 17includes a flange 17 a extending radially outside. The inner peripheralpart of the turbine shell 15 is fixed to the flange 17 a by welding or aplurality of rivets (not shown in the drawings). Additionally, theturbine hub 17 is provided with a spline hole in its inner peripheralpart. The spline hole is engaged with the input shaft of thetransmission (not shown in the drawings).

The stator 5 is configured to regulate the flow of hydraulic oilreturning from the turbine 4 to the impeller 3, and is disposed betweenthe inner peripheral part of the impeller 3 and that of the turbine 4.The stator 5 is mainly composed of a stator carrier 20 and a pluralityof stator blades 21 mounted to the outer peripheral surface of thestator carrier 20. The stator carrier 20 is supported by a stationaryshaft through a one-way clutch 22. It should be noted that thrustbearings 24 and 25 are disposed axially on the both sides of the statorcarrier 20.

(Lock-Up Device 7)

As shown in FIGS. 1 and 2, the lock-up device 7 is disposed in a spacebetween the front cover 2 and the turbine 4. The lock-up device 7includes a clutch unit 28 and a damper portion 29.

<Clutch Unit 28>

As shown in FIGS. 1 and 2, the clutch unit 28 is a multi-plate clutch.The clutch unit 28 includes a plurality of clutch plates 31 (clutchportion), a piston 32, and a support member 35. The support member 35 iscomposed of a sleeve 33 and an oil chamber plate 34.

—Clutch Plates 31—

The plural clutch plates 31 are disposed between the front cover 2 andthe piston 32. The plural clutch plates 31 include two first clutchplates 31 a and two second clutch plates 31 b. The first clutch plates31 a have an annular shape, and likewise, the second clutch plates 31 bhave an annular shape. These two types of clutch plates, i.e., the firstand second clutch plates 31 a and 31 b, are alternately disposed whilebeing aligned in the axial direction. Each first clutch plate 31 a isprovided with a plurality of teeth on its inner peripheral part. Each ofthe first and second clutch plates 31 a and 31 b is provided with afriction facing fixed to one lateral surface thereof. Each of the secondclutch plates 31 b is provided with a plurality of teeth on its outerperipheral part.

—Piston 32—

The piston 32 has an annular shape and is disposed on the transmissionside of the front cover 2. The piston 32 is supported by the supportmember 35 while being movable in the axial direction. The piston 32includes a pressing part 32 a and a plurality of engaging protrusions 32b. The pressing part 32 a is a part for pressing the plural clutchplates 31 toward the front cover 2. The pressing part 32 a is providedon the outer peripheral part of the piston 32 so as to be opposed to theplural clutch plates 31 in the axial direction. The engaging protrusions32 b are provided on the inner peripheral part of the piston 32, andprotrude therefrom to the inner peripheral side. As shown in FIG. 3, theplural engaging protrusions 32 b are provided at predetermined intervalsin the circumferential direction. It should be noted that FIG. 3 is afront view of the piston 32 seen from the front cover 2 side.

—Support Member 35—

The sleeve 33 composes part of the support member 35 and includes anannular protrusion 33 a. The annular protrusion 33 a axially protrudesfrom the front cover 2-side lateral surface of the sleeve 33. Therefore,gaps are produced between the front cover 2 and the sleeve 33, and arelocated on the inner peripheral side and the outer peripheral side ofthe annular protrusion 33 a, respectively. The annular protrusion 33 ais fixed to one lateral surface of the front cover 2 by welding or soforth. Thus, the sleeve 33 is configured to be rotated insynchronization with the front cover 2. Additionally, the sleeve 33 isprovided with a flange 33 b on the turbine 4-side end of its outerperipheral part. The flange 33 b has an annular shape and extendsradially outward.

A drive hub 37 is fixed to the sleeve 33. The drive hub 37 supports thefirst clutch plates 31 a. The drive hub 37 includes a hub body 37 a anda tubular part 37 b. The hub body 37 a has a substantially annular discshape. The tubular part 37 b is formed by bending the outer peripheralpart of the hub body 37 a toward the front cover 2.

The hub body 37 a is fixed to the front cover 2-side lateral surface ofthe sleeve 33. The tubular part 37 b is provided with a plurality ofslits 37 c. The slits 37 c extend in the axial direction, while beingaligned at predetermined intervals in the circumferential direction. Theslits 37 c are opened on the front cover 2 side. The teeth, provided onthe inner peripheral part of the first clutch plates 31 a, are engagedwith the plural slits 37 c. With this construction, the first clutchplates 31 a are non-rotatable relatively to the drive hub 37 (i.e., thesleeve 33) but are movable relatively thereto in the axial direction.

The oil chamber plate 34 composes part of the support member 35 and isdisposed on the turbine 4 side of the piston 32. The oil chamber plate34 includes a body 34 a and a tubular part 34 b. The body 34 a has anannular disc shape. The tubular part 34 b is provided on the outerperipheral part of the body 34 a. The body 34 a is fixed at its innerperipheral part to the flange 33 b of the sleeve 33. The tubular part 34b is formed by bending the outer peripheral part of the body 34 a towardthe front cover 2. Additionally, the outer peripheral part of the piston32 is supported by the tubular part 34 b while being movable in theaxial direction.

<Support Structure for Oil Chamber Plate 34>

The oil chamber plate 34 is fixed at the inner peripheral part of thebody 34 a to the front cover 2-side lateral surface of the flange 33 bof the sleeve 33 by welding. The oil chamber plate 34 is herein a memberfor defining an oil chamber (a first oil chamber C1 to be described)together with the piston 32 therebetween. Therefore, when the hydraulicoil is supplied to the oil chamber, a force acts on the oil chamberplate 34 in a direction separating from the piston 32. However, the oilchamber plate 34 is fixed to the piston 32-side lateral surface of theflange 33 b, i.e., the surface facing in a direction opposite to thedirection that the aforementioned force acts on the oil chamber plate34. Hence, the oil chamber 34, receiving the force generated by ahydraulic pressure, is supported by the flange 33 b. Accordingly,deformation of the oil chamber plate 34 can be inhibited.

<Synchronization Mechanism>

The engaging protrusions 32 b of the piston 32 are engaged with theslits 37 c of the drive hub 37, respectively. With this construction,the piston 32 is configured to be rotated in synchronization with thesleeve 33 and the front cover 2 through the drive hub 37. In otherwords, a synchronization mechanism for rotating the piston 32 insynchronization with the support member 35 is composed of the slits 37 cof the drive hub 37 and the engaging protrusions 32 b of the piston 32.

It should be noted that the slits 37 c and the engaging protrusions 32 bof the piston 32 are engaged over the entire moving range of the piston32. Therefore, even when the piston 32 is moved in the axial direction,the slits 37 c and the engaging protrusions 32 b are not disengaged fromeach other.

<Hydraulic Circuit>

The sleeve 33 is provided with a seal member 51 on its outer peripheralsurface. Thus, the seal member 51 seals between the outer peripheralsurface of the sleeve 33 and the inner peripheral surface of the piston32. On the other hand, the piston 32 is provided with a seal member S2on its outer peripheral surface. The seal member S2 seals between theouter peripheral surface of the piston 32 and the inner peripheralsurface of the tubular part 34 b of the oil chamber plate 34. With theseconstructions, the first oil chamber C1 is defined between the piston 32and the oil chamber plate 34 in order to press the piston 32 toward theclutch plates 31.

The sleeve 33 is provided with a hydraulic circuit. The hydraulic oilsupplied from the inner peripheral part of the turbine hub 17 issupplied to the first oil chamber C1 through the hydraulic circuit. Thehydraulic circuit includes a first oil channel P1, a second oil channelP2 and an oil sump Ph.

The oil sump Ph is provided on the turbine 4-side lateral surface of thesleeve 33. More specifically, a groove 33 c is provided on the turbine4-side lateral surface of the sleeve 33. The groove 33 c is an annulargroove recessed toward the front cover 2. Additionally, a plate 39having an annular shape is fixed to the sleeve 33 so as to cover thegroove 33 c. In other words, the oil sump Ph is defined by the groove 33c and the plate 39.

The first oil channel P1 is provided from the inner peripheral surfaceof the annular protrusion 33 a of the sleeve 33 to the oil sump Ph. Thefirst oil channel P1 is composed of a plurality of holes, each of whichtilts to get closer to the turbine 4 from the inner peripheral side tothe outer peripheral side of the sleeve 33.

The second oil channel P2 is provided whereby the oil sump Ph and thefirst oil chamber C1 are communicated therethrough. The second oilchannel P2 is composed of a plurality of holes. The holes radiallyextend to be orthogonal to the rotational axis.

It should be noted that the entire channel area of the second oilchannel P2 is set to be smaller than that of the first oil channel P1.Additionally, the diameter of each of the holes composing the second oilchannel P2 is smaller than that of each of the holes composing the firstoil channel P1. With the constructions, an orifice effect can be exertedwhen the hydraulic oil flows through the first oil channel P1 and thesecond oil channel P2. Accordingly, the flow rate of the hydraulic oilflowing out of the second oil channel P2 can be inhibited low, andpulsation of the flow rate of an oil pump can be inhibited.Consequently, shock can be alleviated when a clutch-on state is made.Moreover, in the present preferred embodiment, the oil sump Ph isdefined between the first oil channel P1 and the second oil channel P2.Hence, pulsation of the flow rate of the oil pump can be furtherinhibited.

On the other hand, a second oil chamber C2 is defined between the innerperipheral part of the sleeve 33 and the turbine hub 17. The hydraulicoil is supplied to the second oil chamber C2 through a hole 17 bprovided in the flange 17 a of the turbine hub 17. Additionally, thesleeve 33 is provided with a third oil channel P3. The second oilchamber C2 and a space accommodating the clutch plates 31 arecommunicated through the third oil channel P3.

<Damper Portion 29>

The damper portion 29 is configured to attenuate vibration to beinputted thereto through the front cover 2. As shown in FIG. 4, thedamper portion 29 includes an input-side plate 40, inner peripheral sidetorsion springs 41, an intermediate plate 42, outer peripheral sidetorsion springs 43 and a driven plate 44.

—Input-Side Plate 40—

The input-side plate 40 is mounted on the output side of the clutch unit28. Specifically, the input-side plate 40 includes a first side plate 45and a second side plate 46.

The first side plate 45 is the engine-side one of the plates composingthe input-side plate 40. The first side plate 45 includes a first clutchengaging part 45 a extending toward the front cover 2 and a plurality offirst spring engaging parts 45 b.

The first clutch engaging part 45 a has a substantially tubular shape.The first clutch engaging part 45 a is provided with a plurality ofgrooves. The grooves extend in the axial direction while being alignedat predetermined intervals in the circumferential direction. The teethprovided on the outer peripheral part of each second clutch plate 31 bare engaged with the grooves. With this construction, the second clutchplates 31 b and the first side plate 45 are non-rotatable relatively toeach other but are movable relatively to each other in the axialdirection.

The first spring engaging parts 45 b are provided in a part extendedradially inside from the turbine side end of the first clutch engagingpart 45 a. Specifically, the first spring engaging parts 45 b are windowparts disposed at predetermined intervals in the circumferentialdirection. Each first spring engaging part 45 b is provided withcut-and-raised parts. The cut-and-raised parts are formed by cutting andraising the inner peripheral side edge and the outer peripheral sideedge of each first spring engaging part 45 b in the axial direction. Theinner peripheral side torsion springs 41 are disposed in the firstspring engaging parts 45 b, respectively. Additionally, a pair ofcircumferentially opposed walls of each first spring engaging part 45 bis engaged with the both ends of each inner peripheral side torsionspring 41.

The second side plate 46 is the transmission-side one of the platescomposing the input-side plate 40. The second side plate 46 is disposedat a predetermined interval from the first side plate 45 in the axialdirection. The second side plate 46 is fixed to the first side plate 45by a plurality of stud pins 47 so as to be unitarily rotatabletherewith.

The second side plate 46 includes a plurality of second spring engagingparts 46 a. The second spring engaging parts 46 a are window partsdisposed at predetermined intervals in the circumferential direction.The second spring engaging parts 46 a are disposed in axial oppositionto the first spring engaging parts 45 b, respectively. Each secondspring engaging part 46 a is provided with cut-and-raised parts. Thecut-and-raised parts are formed by cutting and raising the innerperipheral side edge and the outer peripheral side edge of each secondspring engaging part 46 a in the axial direction. The inner peripheralside torsion springs 41 are disposed in the second spring engaging parts46 a, respectively. Additionally, a pair of circumferentially opposedwalls of each second spring engaging part 46 a is engaged with the bothends of each inner peripheral side torsion spring 41.

—Inner Peripheral Side Torsion Springs 41—

The plural inner peripheral side torsion springs 41 are disposed inalignment with each other in the circumferential direction.

Each of the inner peripheral side torsion springs 41 is composed of alarge coil spring 41 a and a small coil spring 41 b. The small coilspring 41 b is inserted in the interior of the large coil spring 41 a.The spring length of the small coil spring 41 b is shorter than that ofthe large coil spring 41 a.

Each of the inner peripheral side torsion springs 41 is disposed in eachof the first spring engaging parts 45 b (window parts) of the first sideplate 45, each of the second spring engaging parts 46 a (window parts)of the second side plate 46, and each of third spring engaging parts 42a (window parts) of the intermediate plate 42 to be described. Eachinner peripheral side torsion spring 41 is supported at both of itscircumferential ends and both of its radial ends by the first, secondand third spring engaging parts 45 b, 46 a and 42 a (window parts).Additionally, each inner peripheral side torsion spring 41 is restrictedfrom jumping out by the cut-and-raised parts of each first springengaging part 45 b (window part) and those of each second springengaging part 46 a (window part).

—Intermediate Plate 42—

The intermediate plate 42 is disposed axially between the first sideplate 45 and the second side plate 46. The intermediate plate 42 isrotatable relatively to the first side plate 45, the second side plate46 and the driven plate 44. The intermediate plate 42 is a member forcausing the inner peripheral side torsion springs 41 and the outerperipheral side torsion springs 43 to act in series.

The outer peripheral part of the intermediate plate 42 has asubstantially tubular shape and is opened toward the turbine 4. Thetubular outer peripheral part of the intermediate plate 42 holds theouter peripheral side torsion springs 43. Additionally, fifth springengaging parts 44 b of the driven plate 44 to be described are disposedin the opening of the tubular outer peripheral part.

The intermediate plate 42 includes the plurality of third springengaging parts 42 a, a plurality of fourth spring engaging parts 42 band an elongated hole 42 d.

The third spring engaging parts 42 a are provided in the innerperipheral part of the intermediate plate 42, and are engaged with theinner peripheral side torsion springs 41, respectively. The third springengaging parts 42 a are window parts disposed at predetermined intervalsin the circumferential direction. Each third spring engaging part 42 ais disposed axially between, and in opposition to, each pair of thefirst spring engaging part 45 b and the second spring engaging part 46a. The inner peripheral side torsion springs 41 are disposed in thethird spring engaging parts 42 a, respectively. Additionally, a pair ofcircumferentially opposed walls of each third spring engaging part 42 ais engaged with the both ends of each inner peripheral side torsionspring 41.

The fourth spring engaging parts 42 b are provided in the outerperipheral part of the intermediate plate 42, while being aligned atpredetermined intervals in the circumferential direction. The fourthspring engaging parts 42 b are engaged with the outer peripheral sidetorsion springs 43. Circumferentially adjacent two of the fourth springengaging parts 42 b are engaged with the both ends of each outerperipheral side torsion spring 43. When described in detail,circumferentially adjacent two of the fourth spring engaging parts 42 bare engaged with the inner peripheral parts and the outer peripheralparts of the both ends of each outer peripheral side torsion spring 43.

The elongated hole 42 d has a circumferentially elongated shape. Thestud pins 47 are inserted through the elongated hole 42 d. Whendescribed in detail, the trunk part of each stud pin 47 is insertedthrough the elongated hole 42 d. Under the condition, the both ends ofeach stud pin 47 are fixed to the first side plate 45 and the secondside plate 46. The intermediate plate 42 is attached to the first andsecond side plates 45 and 46 through the stud pins 47, while beingrotatable relatively thereto.

—Outer Peripheral Side Torsion Springs 43—

The plural outer peripheral side torsion springs 43 are disposed inalignment with each other in the circumferential direction.Additionally, the outer peripheral side torsion springs 43 are disposedradially outside the clutch unit 28.

The outer peripheral side torsion springs 43 are held by the outerperipheral part of the intermediate plate 42, and are configured to actin series with the inner peripheral side torsion springs 41 through theintermediate plate 42.

Each outer peripheral side torsion spring 43 is supported at its bothcircumferential ends by circumferentially adjacent two of the fourthspring engaging parts 42 b of the intermediate plate 42. Additionally,each outer peripheral side torsion spring 43 is restricted from jumpingout to the radially outside by the outer peripheral part (tubular part)of the intermediate plate 42, while being interposed betweencircumferentially adjacent two of the fourth spring engaging parts 42 b.Moreover, each outer peripheral side torsion spring 43 makes contact atits both circumferential ends with circumferentially adjacent two of thefifth spring engaging parts 44 b of the driven plate 44.

—Driven Plate 44—

The driven plate 44 is an annular disc member and is fixed to theturbine shell 15. Additionally, the driven plate 44 is rotatablerelatively to the intermediate plate 42.

The driven plate 44 includes a body 44 a, the plural fifth springengaging parts 44 b, a first stopper pawl 44 c and a second stopper pawl44 d.

The body 44 a has a substantially annular shape and is fixed to theturbine shell 15. When described in detail, the body 44 a is fixed tothe turbine shell 15 by fixation means such as welding.

The plural fifth spring engaging parts 44 b are provided on the outerperipheral side of the body 44 a while being integrated with the body 44a. The fifth spring engaging parts 44 b extend axially toward the enginefrom the body 44 a. The fifth spring engaging parts 44 b are engagedwith the outer peripheral side torsion springs 43. The fifth springengaging parts 44 b are formed by bending the outer peripheral part ofthe driven plate 44 axially toward the engine.

The fifth spring engaging parts 44 b are disposed at predeterminedintervals in the circumferential direction. Each outer peripheral sidetorsion spring 43 is disposed between circumferentially adjacent two ofthe fifth spring engaging parts 44 b. Circumferentially adjacent two ofthe fifth spring engaging parts 44 b are engaged with the both ends ofeach outer peripheral side torsion spring 43.

<Stopper Mechanisms>

In the present preferred embodiment, stopper mechanisms are composed ofpart of the intermediate plate 42, part of the second side plate 46, andpart of the driven plate 44. The stopper mechanisms are configured torestrict relative rotation among these plates 42, 46 and 44. The stoppermechanisms will be hereinafter explained in detail.

The intermediate plate 42 is provided with a cutout 42 c in its radiallyintermediate part. The cutout 42 c is provided radially between thethird spring engaging parts 42 a and the fourth spring engaging parts 42b. The cutout 42 c has a circumferentially elongated shape and is openedto the outer peripheral side. On the other hand, the driven plate 44 isprovided with a first stopper pawl 44 c as described above. The firststopper pawl 44 c is inserted into the cutout 42 c.

The first stopper pawl 44 c is provided on the inner peripheral part ofthe driven plate 44, i.e., the inner peripheral part of the body 44 a.The first stopper pawl 44 c is a part extending axially toward theengine from the inner peripheral part of the body 44 a. When describedin detail, the first stopper pawl 44 c is formed by partially bendingthe inner peripheral part of the body 44 a axially toward the engine.

With the aforementioned construction, the intermediate plate 42 isrestricted from rotating relatively to the driven plate 44 by thecontact of the first stopper pawl 44 c with one of the circumferentialend surfaces of the cutout 42 c of the intermediate plate 42. In otherwords, one stopper mechanism is composed of the first stopper pawl 44 cand the cutout 42 c of the intermediate plate 42.

Additionally, the second side plate 46 is provided with a cutout 46 b onits outer peripheral end. The cutout 46 b is opened to the outerperipheral side. On the other hand, the driven plate 44 is provided withthe second stopper pawl 44 d as described above. The second stopper pawl44 d is inserted into the cutout 46 b.

The second stopper pawl 44 d is provided on the inner peripheral part ofthe driven plate 44, i.e., the inner peripheral part of the body 44 a.The second stopper pawl 44 d is formed by partially extending the innerperipheral part of the body 44 a to the further inner peripheral side.

With the aforementioned construction, the first and second side plates45 and 46 are restricted from rotating relatively to the driven plate 44by the contact of the second stopper pawl 44 d with one of the endsurfaces of the cutout 46 b of the second side plate 46. In other words,the other stopper mechanism is composed of the second stopper pawl 44 dand the cutout 46 b of the second side plate 46.

<Positioning Structure for Damper Portion 29>

A structure for positioning the damper portion 29 will be explained withreference to FIG. 5. This positioning structure is provided forpositioning the damper portion 29 in the radial direction and the axialdirection.

In the present preferred embodiment, the turbine shell 15 includes aturbine shell body 50 and a coupling member 51. The turbine blades 16are disposed inside the turbine shell body 50. The coupling member 51 iscoupled at its outer peripheral part to the inner peripheral part of theturbine shell body 50 by rivets 52, while being coupled at its innerperipheral part to the flange 17 a of the turbine hub 17 by welding orrivets (not shown in the drawing). The coupling member 51 includes atubular part 51 a in its radially intermediate part. The tubular part 51a extends in the axial direction.

The tubular part 51 a is provided with a first positioning surface 51 band a second positioning surface 51 c. The first and second positioningsurfaces 51 b and 51 c are formed by cutting or so forth. The firstpositioning surface 51 b has an annular shape and is arranged inparallel to the rotational axis. The second positioning surface 51 c hasan annular shape, and extends radially outward from the turbine 4-sideend of the first positioning surface 51 b while being arrangedorthogonally to the rotational axis.

Additionally, the inner peripheral end surface of the intermediate plate42 of the damper portion 29 makes contact with the first positioningsurface 51 b. Accordingly, the entire damper portion 29 is positioned inthe radial direction. On the other hand, a lateral surface of the innerperipheral end of the intermediate plate 42 makes contact with thesecond positioning surface 51 c. Accordingly, the entire damper portion29 is restricted from moving axially toward the turbine.

Moreover, a restriction plate 54, having an annular disc shape, is fixedto the front cover 2-side lateral surface of the inner peripheral partof the coupling member 51. The restriction plate 54 extends to the outerperipheral side than the inner peripheral end of the first side plate 45of the damper portion 29. Additionally, the front cover 2-side lateralsurface of the first side plate 45 is contactable to the outerperipheral end of the restriction plate 54. With this construction, theentire damper portion 29 is restricted from moving axially toward thefront cover 2.

(Actions)

First, an action of the torque converter body 6 will be explained.During rotation of the front cover 2 and the impeller 3, the hydraulicoil flows from the impeller 3 to the turbine 4, and further flows to theimpeller 3 through the stator 5. Accordingly, a torque is transmittedfrom the impeller 3 to the turbine 4 through the hydraulic oil. Thetorque transmitted to the turbine 4 is transmitted to the input shaft ofthe transmission through the turbine hub 17.

It should be noted that during running of the engine, the hydraulic oilconstantly flows into the second oil chamber C2 through the hole 17 b ofthe turbine hub 17 and is further supplied to the clutch plates 31 andthe impeller 3 through the third oil channel P3.

When the speed ratio of the torque converter 1 increases and rotation ofthe input shaft reaches a predetermined velocity, the hydraulic oil issupplied to the first oil chamber C1 through the first oil channel P1,the oil sump Ph and the second oil channel P2. At this time, thehydraulic pressure in the first oil chamber C1 is higher than that ofthe hydraulic oil supplied to the side on which the clutch plates 31 aredisposed. Accordingly, the piston 32 is moved toward the front cover 2.As a result, the pressing part 32 a of the piston 32 presses the clutchplates 31 toward the front cover 2, whereby a lock-up state (clutch-onstate) is made.

In the aforementioned clutch-on state, a torque is transmitted from thefront cover 2 to the torque converter body 6 through the lock-up device7. Specifically in the lock-up device 7, the torque inputted into thefront cover 2 is sequentially transmitted to the clutch plates 31, thefirst and second side plates 45 and 46, the inner peripheral sidetorsion springs 41 (the large coil springs 41 a and the small coilsprings 41 b), the intermediate plate 42, the outer peripheral sidetorsion springs 43, and the driven plate 44 in this order, and is thenoutputted to the turbine hub 17.

The lock-up device 7 turned into the clutch-on state is hereinconfigured to transmit a torque as described above and simultaneouslyattenuate fluctuation in torque inputted thereto through the front cover2. Specifically, when torsional vibration occurs in the lock-up device7, the inner peripheral side torsion springs 41 and the outer peripheralside torsion springs 43 are configured to be compressed in seriesbetween the first and second side plates 45 and 46 and the driven plate44. Fluctuation in torque, occurring with torsional vibration, is thusattenuated by the activation of the inner peripheral side torsionsprings 41 and the outer peripheral side torsion springs 43.

It should be noted that when the lock-up state is turned off (i.e., aclutch-off state is made), the first oil chamber C1 is configured to beconnected to a drain. Accordingly, the hydraulic oil in the first oilchamber C1 is discharged through the second oil channel P2, the oil sumpPh and the first oil channel P1. In this condition, the hydraulicpressure in the first oil chamber C1 becomes lower than that of the sideon which the clutch plates 31 are disposed. Hence, the piston 32 ismoved toward the turbine 4. As a result, the pressure applied to theclutch plates 31 from the pressing part 32 a of the piston 32 isreleased. Accordingly, the clutch-off state is made.

(Torsional Characteristics)

Next, torsional characteristics will be explained with FIG. 6. In theclutch-on state of the lock-up device 7, a torque inputted through thefront cover 2 is transmitted to the damper portion 29 through the clutchplates 31. At this time, when relative rotation occurs among the firstand second side plates 45 and 46, the intermediate plate 42 and thedriven plate 44 and a torsion angle is produced among them, the outerperipheral side torsion springs 43 and the large coil springs 41 a ofthe inner peripheral side torsion springs 41 are compressed in seriesthrough the intermediate plate 42. Accordingly, a first torsionalstiffness K1 is formed. In FIG. 6, reference sign J1 represents a rangein which a torque with respect to a torsion angle is determined by thefirst torsional stiffness K1.

Next, with increase in torque to be transmitted, a relative rotationangle (torsion angle) increases between the intermediate plate 42 andthe first and second side plates 45 and 46. When the relative rotationangle therebetween becomes a predetermined angle, the small coil springs41 b of the inner peripheral side torsion springs 41 are alsocompressed. In other words, in this condition, the large coil springs 41a of the inner peripheral side torsion springs 41 and the outerperipheral side torsion springs 43 are compressed in series, andsimultaneously, the large coil springs 41 a and the small coil springs41 b of the inner peripheral side torsion springs 41 are compressed inparallel.

A second torsional stiffness K2 is formed by the aforementioned actions.In FIG. 6, reference sign J2 represents a range in which the torque withrespect to the torsion angle is determined by the second torsionalstiffness K2. Subsequently, with further increase in torsion angle, thefirst stopper pawl 44 c of the driven plate 44 makes contact with one ofthe end surfaces of the cutout 42 c of the intermediate plate 42.

With further increase in torque to be transmitted, the relative rotationangle (torsion angle) further increases among the first and second sideplates 45 and 46, the intermediate plate 42 and the driven plate 44 (inthis condition, the intermediate plate 42 and the driven plate 44 arerotated in synchronization with each other). Relative rotation betweenthe intermediate plate 42 and the driven plate 44 is thus prevented inand after the range J2. Hence, the outer peripheral side torsion springs43 are deactivated. In other words, in and after the range J2, the largecoil springs 41 a and the small coil springs 41 b of the innerperipheral side torsion springs 41 are compressed.

A third torsional stiffness K3 is formed by the aforementioned actions.In FIG. 6, reference sign J3 represents a range in which the torque withrespect to the torsion angle is determined by the third torsionalstiffness K3. Subsequently, with further increase in torsion angle, thesecond stopper pawl 44 d of the driven plate 44 makes contact with oneend surface of the cutout 46 b of the second side plate 46. In thiscondition, the large coil springs 41 a and the small coil springs 41 bof the inner peripheral side torsion springs 41 are deactivated.

(Features)

In the aforementioned preferred embodiment, the oil chamber plate 34 isfixed to the piston 32-side lateral surface of the flange 33 b, i.e., alateral surface facing oppositely to a direction in which a force actson the oil chamber plate 34. Therefore, when the oil chamber plate 34receives a force generated by the hydraulic pressure, deformation of theoil chamber plate 34 can be inhibited because the oil chamber plate 34is supported by the flange 33 b. Consequently, without increasing thethickness of the oil chamber plate 34, the amount of deformation of theoil chamber plate 34 can be reduced low with a simple construction.

Other Preferred Embodiments

The present disclosure is not limited to the aforementioned preferredembodiment, and a variety of changes or modifications can be madewithout departing from the scope of the present disclosure.

In the aforementioned preferred embodiment, the oil chamber plate 34 isfixed at its inner peripheral part to the flange 33 b of the sleeve 33.However, the part of the oil chamber plate 34 to be joined to the flange33 b is not limited to the inner peripheral part. For example, theflange 33 b may be extended to the outer peripheral side, and the oilchamber plate 34 may be joined at its radially intermediate part to theextended flange 33 b.

What is claimed is:
 1. A lock-up device for a torque converter, thelock-up device configured to transmit a torque from a front cover to atransmission-side member through a turbine, the lock-up devicecomprising: a clutch portion disposed between the front cover and theturbine; a piston disposed to be movable in an axial direction, thepiston configured to turn the clutch portion into a torque transmissionstate; a sleeve fixed to the front cover, the sleeve including an outerperipheral surface and a protrusion, the outer peripheral surfacesupporting an inner peripheral surface of the piston such that thepiston is movable in the axial direction, the protrusion having anannular shape, the protrusion protruding radially outward from the outerperipheral surface; and an oil chamber plate having a disc shape, theoil chamber plate joined to a piston-side lateral surface of theprotrusion of the sleeve, the oil chamber plate defining an oil chambertogether with the piston therebetween, the oil chamber configured to besupplied a hydraulic oil for activating the piston.
 2. The lock-updevice for a torque converter according to claim 1, wherein the oilchamber plate is joined at an inner peripheral part thereof to theprotrusion of the sleeve by welding.
 3. The lock-up device for a torqueconverter according to claim 1, wherein the oil chamber plate includes atubular part, the tubular part supporting an outer peripheral surface ofthe piston such that the piston is movable.
 4. The lock-up device for atorque converter according to claim 3, further comprising: a pluralityof seal members respectively mounted between the inner peripheralsurface of the piston and the outer peripheral surface of the sleeve andbetween the outer peripheral surface of the piston and an innerperipheral surface of the tubular part of the oil chamber plate, whereinthe sleeve includes an oil channel for supplying the hydraulic oil tothe oil chamber.
 5. The lock-up device for a torque converter accordingto claim 1, further comprising: a drive hub fixed to the sleeve, whereinthe piston includes an engaging part, the engaging part engaged withpart of the drive hub, the piston configured to be rotated insynchronization with the drive hub.